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/******************************************************************************
* common/notifier.c
*
* Routines to manage notifier chains for passing status changes to any
* interested routines.
*
* Original code from Linux kernel 2.6.27 (Alan Cox <Alan.Cox@linux.org>)
*/
#include <xen/config.h>
#include <xen/init.h>
#include <xen/notifier.h>
/**
* notifier_chain_register - Add notifier to a raw notifier chain
* @nh: Pointer to head of the raw notifier chain
* @n: New entry in notifier chain
*
* Adds a notifier to a raw notifier chain.
* All locking must be provided by the caller.
*/
void __init notifier_chain_register(
struct notifier_head *nh, struct notifier_block *n)
{
struct list_head *chain = &nh->head.chain;
struct notifier_block *nb;
while ( chain->next != &nh->head.chain )
{
nb = list_entry(chain->next, struct notifier_block, chain);
if ( n->priority > nb->priority )
break;
chain = chain->next;
}
list_add(&n->chain, chain);
}
/**
* notifier_chain_unregister - Remove notifier from a raw notifier chain
* @nh: Pointer to head of the raw notifier chain
* @n: Entry to remove from notifier chain
*
* Removes a notifier from a raw notifier chain.
* All locking must be provided by the caller.
*/
void __init notifier_chain_unregister(
struct notifier_head *nh, struct notifier_block *n)
{
list_del(&n->chain);
}
/**
* notifier_call_chain - Informs the registered notifiers about an event.
* @nh: Pointer to head of the raw notifier chain
* @val: Value passed unmodified to notifier function
* @v: Pointer passed unmodified to notifier function
* @pcursor: If non-NULL, position in chain to start from. Also updated on
* return to indicate how far notifications got before stopping.
*
* Calls each function in a notifier chain in turn. The functions run in an
* undefined context. All locking must be provided by the caller.
*
* If the return value of the notifier can be and'ed with %NOTIFY_STOP_MASK
* then notifier_call_chain() will return immediately, with teh return value of
* the notifier function which halted execution. Otherwise the return value is
* the return value of the last notifier function called.
*/
int notifier_call_chain(
struct notifier_head *nh, unsigned long val, void *v,
struct notifier_block **pcursor)
{
int ret = NOTIFY_DONE;
struct list_head *cursor;
struct notifier_block *nb;
bool_t reverse = !!(val & NOTIFY_REVERSE);
cursor = &(pcursor && *pcursor ? *pcursor : &nh->head)->chain;
do {
cursor = reverse ? cursor->prev : cursor->next;
nb = list_entry(cursor, struct notifier_block, chain);
if ( cursor == &nh->head.chain )
break;
ret = nb->notifier_call(nb, val, v);
} while ( !(ret & NOTIFY_STOP_MASK) );
if ( pcursor )
*pcursor = nb;
return ret;
}
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